The ion microscope is a particularly sensitive analytical tool for the localization of ions such as sodium, potassium, and calcium which are highly diffusible and of considerable interest in many biological systems. Cryotechniques are being investigated for the preparation of thin sections of tissues which eliminate the possibility of ion loss and redistribution of ions not strongly bound to the biological matrix. The freeze substitution technique will be explored to provide ion images of high quality. Biological standards are being prepared to allow quantification of ion microscopic analysis of tissues. Both doped gelatine and plant and animal tissues are being explored as calibration standards. Digital image processing is being used to perform feature and field analysis of biological sections. Our previous method of digitization of ion micrograph negatives with a microphotodensimeter has been replaced by a direct microscopic image digital acquisition system (MIDAS) which is being evaluated for the study of biological samples in real time. The system employs a low light level TV camera, a video color graphics system, and digital image processing techniques. With appropriate standards, quantitative analysis of individual features will be investigated. A new second generation CAMECA IMS-3F ion microscope is being installed which will provide greater sensitivity and spatial resolution, thereby extending the applicability of the technique for the study of biological systems.